DLC codes are region locked. You cannot use the code you purchased on your account because the code is from one region and your account is another. Your only option is to change your account's region and you'll have to do that through the platform's customer support; based on your code being for Playstation, you'll need to speak to Sony about changing your account's region. Bungie cannot assist you with this. There is nothing else that can be done outside of you simply buying the game properly in your region. I hope the Collector's Edition was worth going through all the trouble, it sounds like a pain to me, but good luck!